This invention relates to an electric power distribution and metering system within a box-like enclosure and more particularly to an apparatus for rejecting improperly installed plug-on units, containing circuit controlling devices, in the enclosure.
There is a trend for electrical codes and certification laboratories for electrical equipment to require that power distribution panels designed for use outdoors such as in mobile home parks, marinas, parking lots and the like with interchangeable plug-on units have a means to assure grounding prior to the live contacts being energized.
The closest prior art believed to be pertinent to the present invention is set forth in the Shallbetter U.S. Pat. No. 3,753,047 and the Boyle U.S. Pat. No. 3,450,951 both of which disclose an outdoor electrical meter box and service outlet to be mounted on a hollow post or the like through which electrical power lines may pass into the meter distribution panel. However, neither patent discloses a means for insuring a ground connection on a plug-on unit before its circuit is energized. A serious drawback to this type of an electrical power distribution and metering system is that the plug-on unit may not be grounded before the live contacts of the circuit are energized and thus create a potential shock hazard.